Systems and methods for signaling and interference detection in sensor devices

Abstract

An input device processing system comprises a sensor module that transmits a first transmitter signal with a transmitter electrode and receives a resulting signal with a receiver electrode. The first transmitter signal comprises a first transmitter frequency, and the resulting signal comprises effects corresponding to the first transmitter signal. A demodulation module demodulates the resulting signal to produce a first signal (e.g., an upper sideband signal) and a second signal (a lower sideband signal), selectably determines a first measurement of a change in capacitive coupling between the transmitter electrode and the receiver electrode based on at least one of the first and second signals, and determines positional information for an input object based on the first measurement.

The invention claimed is: 
     
       1. A processing system for an input device, the processing system comprising:
 a sensor module comprising sensor circuitry, the sensor module configured to transmit a first transmitter signal with a transmitter electrode and receive a resulting signal with a receiver electrode, wherein the first transmitter signal comprises a first transmitter frequency, and the resulting signal comprises effects corresponding to the first transmitter signal; and 
 a demodulation module configured to demodulate the resulting signal to produce first and second output signals, the demodulation module comprising: 
 a first mixing stage comprising a first mixing frequency and a second mixing frequency; and 
 a second mixing stage in series with the first mixing stage and comprising a third mixing frequency and a fourth mixing frequency; 
 wherein the third mixing frequency is a combination of the first mixing frequency and the first transmitter frequency; and 
 wherein the demodulation module is configured to determine a first measurement of a change of capacitive coupling between the transmitter electrode and the receiver electrode based on the first output signal, and to determine positional information for an input object based on the first measurement. 
 
     
     
       2. The processing system of  claim 1 , wherein a measure of interference is determined based on the second output signal. 
     
     
       3. The processing system of  claim 2 , wherein the sensor module is configured to transmit a second transmitter signal, different from the first transmitter signal, based on the measure of interference. 
     
     
       4. The processing system of  claim 1 , wherein the fourth mixing frequency is in quadrature with the third mixing signal, and the second mixing frequency is in quadrature with the first mixing signal. 
     
     
       5. The processing system of  claim 1 , wherein the third mixing frequency is a combination of the first mixing frequency and the first transmitter frequency such that the third mixing frequency corresponds to the absolute value of the difference between the first mixing frequency and the first transmitter signal. 
     
     
       6. The processing system of  claim 1 , wherein the first mixing stage comprises a harmonic rejection mixer. 
     
     
       7. The processing system of  claim 1 , wherein the demodulation module further comprises a first filter stage coupled to the first mixing stage and a second filter stage coupled to the second mixing stage. 
     
     
       8. The processing system of  claim 7 , wherein the first filter stage comprises an image reject filter. 
     
     
       9. The processing system of  claim 1 , wherein:
 the demodulation module further comprises a third mixing stage comprising a fifth mixing frequency and a sixth mixing frequency, wherein the fifth mixing frequency is in quadrature with third mixing frequency, and the sixth mixing frequency is in quadrature with the fourth mixing frequency; 
 the demodulation module is further configured to demodulate the resulting signal to produce a first quadrature signal and a second quadrature signal, wherein the first quadrature signal is in quadrature with the first output signal, and the second quadrature signal is in quadrature with the second output signal; and 
 the demodulation module is further configured to determine interference of the first quadrature signal and interference of the second quadrature signal. 
 
     
     
       10. The processing system of  claim 9 , wherein sensor module is configured to transmit a second transmitter signal, different from the first transmitter signal, based on at least one of the interference of the first quadrature signal and the interference of the second quadrature signal. 
     
     
       11. The processing system of  claim 1 , wherein the demodulation module is further configured to determine a second measurement of a change in capacitive coupling between the transmitter electrode and the receiver electrode based on the second output signal, and wherein positional information for an input object is further based on the second measurement. 
     
     
       12. A capacitive sensor device comprising:
 a transmitter electrode; 
 a receiver electrode; and 
 a processing system communicatively coupled to the transmitter electrode and the receiver electrode, the processing system comprising a first mixing stage comprising a first mixing frequency and a second mixing frequency, and a second mixing stage in series with the first mixing stage and comprising a third mixing frequency and a fourth mixing frequency, wherein the third mixing frequency is a combination of the first mixing frequency and the first transmitter frequency, the fourth mixing frequency is in quadrature with the third mixing signal, and the second mixing frequency is in quadrature with the first mixing signal; 
 wherein the processing system is configured to: 
 transmit a first transmitter signal with the transmitter electrode and receive a resulting signal with the receiver electrode, wherein the first transmitter signal comprises a first transmitter frequency, and the resulting signal comprises effects corresponding to the first transmitter signal; 
 demodulate the resulting signal to produce first and second output signals; and 
 determine a first measurement of a change of capacitive coupling between the transmitter electrode and the receiver electrode based on the first output signal, and to determine positional information for an input object based on the first measurement. 
 
     
     
       13. The capacitive sensor device of  claim 12 , wherein a measure of interference is determined based on the second output signal, and the sensor module is configured to transmit a second transmitter signal, different from the first transmitter signal, based on the measure of interference. 
     
     
       14. The capacitive sensor device of  claim 12 , wherein the third mixing frequency is a combination of the first mixing frequency and the first transmitter frequency such that the third mixing frequency corresponds to the absolute value of the difference between the first mixing frequency and the first transmitter signal. 
     
     
       15. The capacitive sensor device of  claim 12 , wherein the processing system further comprises a first filter stage coupled to the first mixing stage and a second filter stage coupled to the second mixing stage. 
     
     
       16. The capacitive sensor device of  claim 12 , wherein:
 the processing system further comprises a third mixing stage comprising a fifth mixing frequency and a sixth mixing frequency, wherein the fifth mixing frequency is in quadrature with third mixing frequency, and the sixth mixing frequency is in quadrature with the fourth mixing frequency; 
 the processing system is further configured to demodulate the resulting signal to produce a first quadrature signal and a second quadrature signal, wherein the first quadrature signal is in quadrature with the first output signal, and the second quadrature signal is in quadrature with the second output signal; and 
 the processing system is further configured to determine interference of the first quadrature signal and interference of the second quadrature signal. 
 
     
     
       17. A method of capacitive sensing, the method comprising:
 transmitting a first transmitter signal with a transmitter electrode, the first transmitter signal comprising a first transmitter frequency; 
 receiving a resulting signal with a receiver electrode, the resulting signal comprising effects corresponding to the first transmitter signal; 
 demodulating the resulting signal to produce a first output signal and a second output signal by mixing the resulting signal with a first mixing stage and a second mixing stage in series with the first mixing stage, wherein the first mixing stage comprises a first mixing frequency and a second mixing frequency and the second mixing stage comprises a third mixing frequency and a fourth mixing frequency, and wherein the third mixing frequency corresponds to the absolute value of the difference between the first mixing frequency and the first transmitter frequency; 
 determining a first measurement of a change of capacitive coupling between the transmitter electrode and the receiver electrode based on the first output signal; and 
 determining positional information for an input object based on the first measurement. 
 
     
     
       18. The method of  claim 17 , further comprising:
 determining a measure of interference based on the second output signal, and 
 transmitting a second transmitter signal, different from the first transmitter signal, based on the measure of interference. 
 
     
     
       19. The method of  claim 17 , further comprising:
 demodulating the resulting signal to produce a first quadrature signal and a second quadrature signal, wherein the first quadrature signal is in quadrature with the first output signal, and the second quadrature signal is in quadrature with the second output signal; and 
 determining interference of the first quadrature signal and interference of the second quadrature signal. 
 
     
     
       20. The method of  claim 19 , further comprising transmitting a second transmitter signal, different from the first transmitter signal, based on at least one of the interference of the first quadrature signal and the interference of the second quadrature signal.